/usr/share/gtk-doc/ is in xfce4-panel-dev 4.12.2-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/gtk-doc/html/
/usr/share/gtk-doc/html/libxfce4panel-1.0/
/usr/share/gtk-doc/html/libxfce4panel-1.0/XfceArrowButton.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/XfceHVBox.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/XfcePanelImage.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/XfcePanelPlugin.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/api-index-4-6.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/api-index-4-8.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/api-index-deprecated.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/api-index-full.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/home.png
/usr/share/gtk-doc/html/libxfce4panel-1.0/index.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/left-insensitive.png
/usr/share/gtk-doc/html/libxfce4panel-1.0/left.png
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-1.0.devhelp2
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-Commonly-used-plugin-macros.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-Convenience-Functions.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-GObject-Oriented-Panel-Plugin-Registers-Macros.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-Panel-Plugin-Register-Macros-(4.6-Style).html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-Panel-Plugin-Register-Macros.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-Standard-Enumerations.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-Version-Information.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-fundamentals.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-miscelleanous.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-plugins.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/libxfce4panel-widgets.html
/usr/share/gtk-doc/html/libxfce4panel-1.0/right-insensitive.png
/usr/share/gtk-doc/html/libxfce4panel-1.0/right.png
/usr/share/gtk-doc/html/libxfce4panel-1.0/style.css
/usr/share/gtk-doc/html/libxfce4panel-1.0/up-insensitive.png
/usr/share/gtk-doc/html/libxfce4panel-1.0/up.png